Transcript Energy Organelles & the Cytoskeleton

Energy Organelles &
the Cytoskeleton
Section 6.5, 6.6, and 6.7
Convert energy to forms the cell can use
for work
 Mitochondria – site of cellular respiration
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◦ Found in plants & animals
◦ Process that makes ATP from food
◦ Oxygen is needed
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Chloroplasts – site of photosynthesis
◦ Found in plants & algae only
◦ Convert solar energy to chemical energy
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Both enclosed by membranes
Mitochondria & Chloroplasts
Membranes are made on free ribosomes
 Contain their own ribosomes
 Contain a small amount of DNA
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Mitochondria & Chloroplast
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Found in all Eukaryotic cells
A cell can have hundreds to thousands of
mitochondria depending on its function
Move around, change shape & divide
Surrounded by a double membrane
Outer membrane smooth
Inner membrane folding (Cristae)
◦ Increases surface area
Intermembrane space
 Matrix
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Mitochondria
Mitochondria Sturcture
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Member of the plant organelle group
plastids
◦ Amyloplasts – colorless that store starch in
roots and tubers
◦ Chromoplasts – pigments that give fruits and
flowers orange & yellow colors
◦ Chloroplasts – contain the green pigment
chlorophyll
Chloroplasts
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Double membrane separated by
intermembrane space.
Thylakoids are flattened stacks of sacs
like pancakes or poker chips
Each stack is called a granum (grana)
Fluid outside the thylakoids is the stroma
(space)
Chloroplasts grow, move, & divide
Chloroplasts
Single membrane
 Contain enzymes that transfer hydrogen
from various substances to oxygen
 Hydrogen peroxide is produced (H2O2)
 Functions
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◦ Break fatty acids down
◦ Detoxify alcohol
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H2O2 is converted to water because it is
toxic to the cell
Peroxisomes
Peroxisome structure (TEM)
A network of fibers extending throughout
the cytoplasm
 Plays a role in organizing the structures &
activities of the cell, supporting the cell,
and maintaining its shape
 Composed of three types of structures
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◦ Microtubules
◦ Microfilaments
◦ Intermediate filaments
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Differ in size
Cytoskeleton
Cytoskeleton
Gives support
 Helps the cell maintain shape
 Provides anchorage for organelles
 Can be dismantled and reassembled in a
new location changing the shape of the
cell
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Cytoskeleton - Support
Changes in cell location
 Movements of parts of the cell
 Interaction of cytoskeleton with motor
proteins
 Examples:
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Movements of cilia & flagella
Muscle cell contraction
Movement of vesicles on “monorail”
Cytoplasmic streaming
Cytoskeleton - Motility
Motor Proteins
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Cytoskeleton can transmit mechanical
forces exerted by extracellular molecules
via surface proteins of the cell to the
interior and even the nucleus
Cytoskeleton - Regulation
Microtubules – thickest of the three
 Microfilaments – thinnest of the three
 Intermediate filaments – middle range
size filaments
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3 Types of Fibers
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Hollow rods
Made from protein tubulin (alpha & beta)
Shape and support the cell
Serve as tracks for motor proteins
Examples:
◦ Guide secretory vesicles from the golgi to the
plasma membrane
◦ Responsible for the separation of chromosomes
during cell division
Microtubules
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Microtubules grow out from centrosomes
“Microtubule-organizing center”
Animal cells contain a pair of centrioles
found at right angles to each other
Each composed of 9 sets of triplet
microtubules arranged in a ring
Before the cell divides the centrioles
replicate
Help in organizing microtubules but not
essential
Plants lack centrioles
Centrosomes & Centrioles
Specialized arrangement of microtubules
is responsible for beating of cilia & flagella
 Flagella
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◦ 1-2 per cell, undulating motion
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Cilia
◦ Large numbers on cell surface, work like oars
Both are made from 9+2 arrangement
 Dynein arms responsible for bending
movements of cilia & flagella
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◦ Similar to a cat walking up a tree
Cilia & Flagella
Motion of Flagella & Cilia
9+2 arrangement of cilia &
flagella
Dynein “walking”
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Solid rods
Also called actin filaments because they
are built from actin protein
Twisted double chain of actin subunits
Function is to bear pulling forces
Part of the contractile apparatus of muscle
cells
Actin & myosin (thicker than actin)
interact to produce muscle contraction
Microfilaments (Actin filaments)
Role of Microfilaments & motility
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Mid size filament
Specialized for bearing tension
Very diverse (keratins)
More permanent fixtures of cells
Important in reinforcing the shape of a
cell and fixing the position of certain
organelles
Intermediate Filaments
Things beyond the plasma membrane
 Plants – cell wall
 Animals – Extracellular matrix (ECM)
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Extracellular components
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Protects
Maintains shape
Prevents excess uptake of water
Thicker than plasma membrane
Strong fibers in a matrix formation like
fiberglass make it extremely strong
Layers of cell wall are made that include
pectin (thickening agent in jams & jellies),
cellulose, & hardening substances.
Plant Cell Wall
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Glycoproteins – proteins with
carbohydrate chains
Collagen – accounts for ½ total protein
found in the body
Proteoglycans – Collagen is embedded in
Fibronectin – attaches the ECM to
integrins
Integrins – span the membrane
Important communication from the cell to
its surroundings
Extracellular Matrix of Animals
Extracellular Matrix
Plants – Plasmodesmata
 Channels between cell walls that allow
neighboring cells to communicate with
one another
 Water & small solutes can pass freely
from cell to cell
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Intercellular Junctions
Plant Plasmodesmata
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Animals
◦ Tight junctions – form continuous seals around
the cells – prevent leakage
◦ Desmosomes – fasten cells together into strong
sheets - anchoring
◦ Gap junctions – communicating junctions –
provide cytoplasmic channels from one cell to
an adjacent cell
Intercellular Junctions
Animal cell junctions
Macrophage eating bacteria